The invention relates to a cartridge system for mixing and applying a mixing ware, in particular a medical cement, comprising at least two cartridges that are arranged parallel to each other, and an outlet opening, whereby the cartridges each comprise at least one opening that connect(s) the cartridges to the outlet opening, and the cartridges are bordered laterally through cartridge walls and each comprise a feed plunger for expelling starting components of the mixing ware from the cartridges through the openings, and whereby at least two feed plungers are fixedly connected to each other.
Cartridge systems for mixing and applying a mixing ware can consist of multiple components and are to ensure safe storage and safe closure for components in at least two cartridges prior to their use. The cartridge system should be safe and easy to open right before the application of the mixing ware, whereby synchronous opening of the individual cartridges is desirable.
Reactive pasty two- or multi-component systems must be stored separately after their production and until their application in order to prevent premature, inadvertent reactions of the components. Cartridge systems for the application of pasty two- or multi-component systems have been known for decades. The following documents are cited for exemplary purposes, CH 669 164 A5, EP 0 607 102 A1, EP 0 236 129 A2, DE 3 440 893 A1, U.S. Pat. No. 4,690,306 A, US 2009/062808 A1, EP 0 787 535 A1, WO 2006/005 206 A1, EP 0 693 437 A1, EP 0 294 672 A, EP 0 261 466 A1, and EP 2 008 707 A1. The pasty two- or multi-component systems are mixed right before their application, usually through the use of static mixers. The following documents are cited for exemplary purposes, GB 1,188,516 A, U.S. Pat. No. 2,125,245 A, U.S. Pat. No. 5,968,018 A, U.S. Pat. No. 4,068,830 A, US 2003/179648 A1, EP 0 664 153 A1, and EP 0 289 882 A1. After the cartridges are filled with reactive pastes, the cartridges need to remain safely closed until their application. In this context, mobile plungers, which are also used to dispense the cartridge content, usually seal the cartridge floors.
A number of solutions have been proposed for closing the cartridge system head of the cartridge system. One simple, but very effective, principle is to close the cartridge head with a closure that can be rotated (EP 0 431 347 A1, DE 2 017 292 A1, U.S. Pat. No. 3,215,298 A). The closure is unscrewed prior to the application. Subsequently, a dispensing tube is screwed into a thread on the cartridge head or fixed through a peg system that simulates a thread. In the interim between the cartridges being opened and the dispensing tube being inserted, ingredients of the pastes may evaporate, especially if the pastes contain volatile substances.
The closure that is in very common use currently in the adhesives and sealant industry is based on the wall material of the cartridge being provided to be very thin at the cartridge head such that said wall can be perforated easily.
The backside of the cartridges is usually closed by mobile plungers that are designed for expelling the pastes during application. In the case of humidity- and air-sensitive pastes, aluminium cartridges may be used that are closed by plastic plungers and over which aluminium cylinders that are closed on one side are pressed in for sealing purposes. During the application of the pastes, the aluminium cylinder having one closed side is moved jointly with the plunger towards the front in the direction of the cartridge head through the action of cartridge applicator guns and the paste is expelled in the process. However, any contact of paste and aluminium surfaces may be problematic in medical applications.
Using cartridge systems for sterile pasty medical products, there is a need for not only the pastes, but obviously the cartridges and secondary packaging means also to be provided in sterile form to the user. For example after aseptic filling of the previously sterilised cartridges, these may be transferred directly to sterile packaging means. Moreover, it may make sense for certain products to sterilise the surfaces of filled cartridges jointly with the packaging means after packaging is completed. Aside from gamma sterilization, which cannot be used with paste systems that can be polymerised, there is the option to use ethylene oxide gas for sterilization.
However, one issue of said sterilization with gas in the case of paste systems containing monomers with a high vapour pressure is that a fraction of the monomers in the cartridges evaporates after the actual sterilization, when the residual ethylene oxide is removed by the action of a vacuum, whereby the monomers form a gas phase in the cartridges and can thus exert a pressure against the plungers. This means that the plungers are moved in the direction of the cartridge floors in undesired manner and may be expelled from the cartridges in the extreme case such that the pastes may leak out.
With regard to the application of bone cements for fixation of total joint endoprostheses, it is always necessary to take into consideration that the OR staff is under time pressure during these surgeries. Therefore, as a matter of principle, cartridge systems for medical applications involving the application of paste-like polymethylmethacrylate bone cements should be designed such that they are largely resistant to user errors and can be operated rapidly and safely even in stressful situations.
The methylmethacrylate monomer is an essential ingredient of paste-like polymethylmethacrylate bone cements. Said monomer evaporates readily and has a relatively high vapour pressure at room temperature. For this reason, it is essential to note with regard to the use of methylmethacrylate-containing pastes that the cartridge plungers in the cartridges may be moved and may be expelled from the cartridges in the extreme case by the evaporating methylmethacrylate upon exposure to a vacuum, such as during the degassing as part of ethylene oxide sterilization.
Polymethylmethacrylate bone cements have been in use in medicine for decades for permanent mechanical fixation of total joint endoprostheses. They are based on powder-liquid systems. Recently, polymethylmethacrylate bone cements that are based on the use of cement pastes have been proposed as well (DE 10 2007 050 762 A1, DE 10 2008 030 312 A1, DE 10 2007 052 116 A1). Cartridge systems comprising at least two cartridges having one feed plunger each are well-suited for this type of starting components of mixing wares. In order to achieve homogeneous mixing of the starting components, it is necessary to shift the feed plungers in parallel. For this purpose, it has been proposed to connect the feed plungers of the two cartridges at their ends protruding from the cartridges.
A generic cartridge system of this type having two cartridges and two feed plungers that are connected to each other is known from U.S. Pat. No. 4,260,077 A. Basically, the cartridge system is structured alike two syringes that are situated right next to each other and whose feed plungers can be connected to each other at the end that is on the side of the cartridge floor. A common outlet opening for both cartridge contents is provided on the tip of the cartridge system. When the contents are squeezed out, the feed plungers are pressed into the cartridges until the front ends of the feed plungers touch against the cartridge heads or until the connection of the feed plungers touches against the cartridge walls on the cartridge floor.
This is disadvantageous in that the feed plungers cannot be propelled through the application of pressure to the cartridge floor, i.e. through a compressed gas. For automatic propulsion of the feed plungers, a mechanical propelling mechanism needs to be provided.